1. Technical Field
The present invention relates to an apparatus for preheating a batch of glass cullet which is preferably enriched with raw materials for glass production, comprising a bunker preferably having flow ducts for the passage of warm (off)gas.
2. Prior Art
An apparatus of this type is known, for example, from German Patent No. DE 34 16 317 C2. During the glass production process, this apparatus serves to utilize the thermal energy of the offgases produced during the combustion of the raw materials in the melting furnace for preheating the batch of glass cullet. For this purpose, the offgases are generally guided along flow ducts through the bunker, specifically through the batch of glass cullet—if appropriate in that they have preheated the combustion air required for the melting operation beforehand after they have passed through a heat exchanger. Within the bunker, at least some of the thermal energy of the offgas is transferred to the batch of glass cullet. The preheating of the batch of glass cullet ultimately reduces the amount of thermal energy needed for the downstream melting operation in the melting furnace.
After the batch of glass cullet has flowed through the bunker, it is discharged from the preheater apparatus and fed to the actual melting furnace. However, the discharge of the preheated batch of glass cullet from the preheater is problematic.
This is the case particularly when the batch of glass cullet is to be fed to a melting furnace having a so-called horseshoe fired furnace. This is because the doghouse of the horseshoe fired furnace—the batch feeder alcove of the melting end for feeding the batch of glass cullet—has comparatively small dimensions for design reasons. Therefore, as a rule only one individual chute of a batch feeder can open out into the doghouse of the horseshoe fired furnace, and this chute conveys the batch of glass cullet originating from the preheater apparatus into the doghouse.
In order to produce a continuous flow of material using only one chute, the material discharge capacity of the preheater has to be correspondingly high and constant. It is known in the prior art to use so-called vibrating bases for this purpose in the base region of the preheater. These perform oscillating motions and ensure that the material is discharged as uniformly as possible from the preheater apparatus or that the material discharge capacity of said apparatus is as high as possible. Here, the hoppers open out into the chute of the batch feeder, which in turn opens out into the doghouse.
A disadvantage of this prior art solution is that caking of the warm batch of glass cullet frequently occurs despite the oscillating motions of the vibrating bases. The hoppers accordingly become blocked. As a last consequence, the material discharge is stopped erroneously.